Crop row markers for tractor-drawn implement bars are known in the prior art. In one prior art device, a pair of marker assemblies are mounted for vertical swinging movement on the opposite ends of an implement bar which may be carried by a farm tractor. A single hydraulic cylinder is employed with a pair of pivoted control arms and chains to raise or lower the marker assemblies. Cooperating latch bars pivoted to the control arms are equipped with cam plates which are engaged and influenced by cams on a rotational latch release cam shaft. Over-dead-center stops and rotational biasing means for the cam shaft in the form of a spring is also required.
The objective of this invention is to improve on the prior art in general and the above mentioned device in particular by the provision of a single hydraulic cylinder actuated marker mechanism whose alternately operating latch and release means is greatly simplified and operated in part by gravity and in part by direct cooperative engagement of two pivoted latch bars on the marker control arms of the device. The need for rotational cam elements, shafts, springs or other external biasing and operating means is eliminated in the invention and a much simpler and more positive and direct mode of operation is achieved with fewer parts and with no loss of function due to the elimination of parts. The construction is more sturdy and considerably more economical to build. Parts are eliminated which could become non-operational due to rusting or fouling with mud or debris. The latch bars for the alternately active and inactive row markers are direct in their cooperation and each directly engages a combined stationary latch bar camming and keeper element in a unique and simplified mode of operation under control of the single extensible and retractable hydraulic cylinder which interconnects the two control arms on which the pivoted latch bars are mounted.
A simplified and economical mechanism forming the essence of the invention is also more reliable and efficient in operation than the corresponding means of the prior art.
Other features and advantages of the invention will become apparent during the course of the following detailed description.